Challenge: The patient is a 16 month old male. How should the results of the following hemoglobin electrophoresis be interpreted?
By alkaline gel electrophoresis: 59.5% hemoglobin A0.6% hemoglobin F36.6% hemoglobin S
By cation-exchange HPLC BioRad D-10 (Extended Program): hemoglobin A2 = 3.6% reference interval: =<3.5%
Answer: The ratio of hemoglobin A to S is normally approximately 60:40 which is typical of sickle trait. As well, typical of sickle trait, is a normal hemoglobin (11.5 g/dL; reference interval: 9.5 - 13.5) and hemocrit (35.2%; reference interval: 29-41). However the low MCV (69.2 fL; reference interval: 74 - 108) and elevated RBC count (5.09 million/uL; reference interval: 3.1 - 4.5) are consistent with a co-existent thalassemia. Even though the hemoglobin A2 is marginally elevated (3.6% by HPLC D-10; reference interval: =<3.5%), the ratio of A to S is not compatible with sickle/beta+ thalassemia. This suggests that if thalassemia is present along with sickle cell trait, the most likely type of thalassemia is co-existent alpha thalassemia. Whereas iron deficiency can reduce the MCV, iron deficiency does not increase the RBC count as is the case in this patient, again favoring some type of thalassemia. Unfortunately iron studies were not available for this patient. We recommended that globin chain analysis be performed.